I just learned about Vector, it's a typed Array for Actionscript 3, like generics in Java or C#. However, in Actionscript 3, Vector is a one-off: it's the only class that uses the generics syntax, and developers cannot use generics in their own classes. Nevertheless, Vector gives a type-safe alternative to Array and promises big performance gains. Given that it can also give the type of the containing elements at runtime, I can use it now to drive JSON deserialization into objects too.